1. Field of the Invention
Exemplary aspects of the present disclosure generally relate to an optical scanner and an image forming apparatus including same.
2. Description of the Related Art
Related-art image forming apparatuses, such as copiers, facsimile machines, printers, or multifunction printers having at least one of copying, printing, scanning, and facsimile capabilities, typically form an image on a recording medium according to image data. Thus, for example, a charger uniformly charges a surface of an image bearing member; an optical writer projects a light beam onto the charged surface of the image bearing member to form an electrostatic latent image on the image bearing member according to the image data; a developing device supplies toner to the electrostatic latent image formed on the image bearing member to render the electrostatic latent image visible as a toner image; the toner image is directly transferred from the image bearing member onto a recording medium or is indirectly transferred from the image bearing member onto a recording medium via an intermediate transfer member; a cleaning device then cleans the surface of the image carrier after the toner image is transferred from the image carrier onto the recording medium; finally, a fixing device applies heat and pressure to the recording medium bearing the unfixed toner image to fix the unfixed toner image on the recording medium, thus forming the image on the recording medium.
Typically, an image forming apparatus is equipped with an optical writing unit serving as an optical scanner to form a latent image on an image bearing member, for example, a photoconductive drum. The optical writing unit illuminates and scans the image bearing member with a light beam also known as a write light based on image information. Subsequently, the latent image is developed with toner, thereby forming a visible image, also known as a toner image.
Generally, such an optical writing unit includes a light source to project the light beam, optical parts such as a collimating lens, a scanning lens, a reflective mirror, and a polygon mirror. The light beam projected from the light source such as a laser diode (LD) passes through the collimating lens attached to a housing of the optical writing unit. The collimating lens shapes the light beam into a desired shape. Then, the light beam strikes the polygon mirror. The light beam is deflected and scanned by the polygon mirror, and passes through the scanning lens, the reflective mirror, and so forth. Ultimately, the light beam illuminates the image bearing member. In general, the collimating lens is fixed directly to the housing an adhesive agent.
Due to heightened awareness of environmental problems in recent years, there is increasing market demand for recycling the optical parts used in the optical writing unit. However, the optical parts such as the collimating lens are fixed directly and firmly to the housing adhesives to prevent the optical parts from displacement during and/or after shipment, thereby complicating efforts to separate the optical parts from the housing for recycling. For example, the optical parts need to be handled directly and separated forcibly.
The optical parts have finely processed surfaces that receive or project light so as to obtain certain optical characteristics. Such optical parts are very sensitive to damage and mechanical stress. When separating the optical parts from the housing upon recycling, the optical parts may be damaged, causing undesirable changes in the optical characteristics of the optical parts. For this reason, the optical parts are difficult to recycle, and hence are usually discarded.
To address such a difficulty, JP-2001-111155-A, for example, proposes a collimating lens removably attached to a light source unit. More specifically, the collimating lens is held by a lens barrel serving as a lens holder, and the lens barrel holding the collimating lens is fixed to the light source unit. When removing the collimating lens from the light source unit, the lens barrel is handled directly and separated from the light source unit. With this configuration, the lens barrel is the only place that is directly handled and separated from the light source unit or the housing, thereby preventing the lens surface of the collimating lens from getting damaged. Further, no stress is applied to the collimating lens upon separation from the light source unit. As a result, fluctuation of the optical characteristics of the collimating lens is prevented, and hence the collimating lens can be recycled.
As is generally the case for the collimating lens, when a configuration of the optical scanner, for example, a beam spot diameter, changes, the external diameter of the collimating lens changes accordingly. According to the related art, the inner diameter of the lens barrel for the collimating lens is almost the same as the external diameter of the collimating lens, and the collimating lens is inserted into the lens barrel. Consequently, if the external diameter of the collimating lens changes, a different lens barrel is needed to accommodate the collimating lens in a different size, thus increasing cost of manufacturing and necessitating management of different lens barrels. More specifically, a manufacturing line for different lens barrels or the holders needs to be established, resulting in a significant cost increase.
In view of the above, there is an unsolved need for optical parts that can be recycled easily and inexpensively without getting damaged.